AC3 problems

[wurz]

Hi,

I'm having problems getting my receiver to decode AC3 when outputted from my MacBook. I have verified my receiver and MacBook work correctly as the receiver decodes AC3 just fine when I play films using VLC. When I try using XBMC, there is no sound; the receiver does not detect the AC3 signal. When played thru the MacBook's speakers I get static noise, as expected.

My Audio Output is set to Digital. I'm not sure what else to tinker with in xbmc to get this to work. Any ideas?

This is what I get in the terminal when playing an AC3 encoded film:

Applications wurz$ ./XBMC.app/Contents/MacOS/XBMC
WARNING: The XBMC_HOME environment variable is not set.
++ WARN: could not retrieve file info for `image.nrg': No such file or directory
++ WARN: can't open nrg image file image.nrg for reading
Input #0, avi, from '/Volumes/D$/Video/_Recent/Inland.Empire.avi':
Duration: 02:52:18.0, start: 0.000000, bitrate: 1128 kb/s
Stream #0.0: Video: mpeg4, yuv420p, 640x336 [PAR 1:1 DAR 40:21], 25.00 tb(r)
Stream #0.1: Audio: ac3, 48000 Hz, 5:1, 384 kb/s
Asked to open device: [S/PDIF]
Asked to create device: [S/PDIF]
Device should be digital: [1]
Channels: [2]
Sample Rate: [48000]
BitsPerSample: [16]
PacketSize: [2048]
Considering: [Built-in Output]

[elan]

Originally Posted by wurz

When played thru the MacBook's speakers I get static noise, as expected.

My Audio Output is set to Digital. I'm not sure what else to tinker with in xbmc to get this to work. Any ideas?

The long answer is that I kind of cheat when doing audio passthrough. Portaudio uses an AudioUnit underneath the covers, and when doing passthrough you really shouldn't. Fortunately it seems to work well in most cases. I did read about one person having a short burst of static before the receiver said "Hey, this is encoded audio, what am I doing?"

There are a few things you can check, but it really *should* work. Run the Audio MIDI Setup application, and make sure the Audio Output settings look right for digital output. XBMC should be setting sample rate and bits per sample correctly, but you can make sure they look right. Make sure that no other programs are running that use Audio (and maybe direct your sound effects to go elsewhere). I'm sure this is obvious, but try a few different videos, if you haven't already.

That's about all I can recommend. Most people have gotten passthrough to work, so unless you have an extremely finicky receiver, there could be something wrong with your OS X settings. From the sounds you're hearing, it's trying to dump encoded digital audio out.

(And yes, it is in my longer term plans to rewrite the passthrough code, but it doesn't seem like a high priority now because the vast majority of people are seemingly able to use it perfectly.)


-elan

[wurz]

Thanks for the reply...still not having any luck. it seems the settings in Audio MIDI Setup change automatically when an app outputs to digital. If I tinker in there xbmc tends to hang when playing a film. The settings match what's in the terminal output anyhow.

Sometimes if I pull the optical cable out and in I get the static noise thru my receiver, and then it drops. Was thinking about the "Passthrough Outpt Device" setting in Audio Hardware. This is currently on S/PDIF, but you can enter anything. Should I have it so it matches my audio ouput device name in OSX?

Don't think my receiver is particularly fussy...it never complained with xbmc on the xbox!

[elan]

Originally Posted by wurz

Sometimes if I pull the optical cable out and in I get the static noise thru my receiver, and then it drops. Was thinking about the "Passthrough Outpt Device" setting in Audio Hardware. This is currently on S/PDIF, but you can enter anything. Should I have it so it matches my audio ouput device name in OSX?

Hearing static means that encoded digital output is being sent. If your receiver isn't able to lock onto it, it means that either the stream is being compromised (by a sample rate conversion, e.g.) or that your receiver is really picky about the stream and somehow using the AudioUnit is breaking things.

-elan

[fatez]

Hey man!

I've the same problem with my MiniMac Intel.

VLC and AC3 sounds good, but Qt or OsXbmc sounds linke a "trrrrrrr"




i'm no happy

[elrod]

I'm still trying to get my HD .mkv files to run. From what I understand it works in most cases, except mine... I'm no expert in coding or anything, just an advanced end-user. Like all the others, VLC runs perfect sound, but XBMC doesnt.
Here are my specs:

2Ghz Intel Core 2 Duo MacMini
1GB RAM

running video from an old G4 server.

XBMC version 0.1.4

and the link to my log:
xbmc.log

[Albo]

Originally Posted by elrod

I'm still trying to get my HD .mkv files to run. From what I understand it works in most cases, except mine... I'm no expert in coding or anything, just an advanced end-user. Like all the others, VLC runs perfect sound, but XBMC doesnt.

Do you have any other apps running when trying to play these files? i found that if iTunes was active, I'd get static from mkvs playing in XBMC. As soon as I quit iTunes, the digital sound would pass through to my receiver just fine.

[elrod]

No I'm not running any other apps. Just XBMC.
It's hooked up with an optical cable to my Creative Inspire 5.1 receiver.

When playing .mkv files through VLC they just play fine, when I play the same from within XBMC, no sound at al (with digital set as output, when set to analog video starts playing faster and still no sound)

When I play from vlc in my MacBook, everything plays fine as well, but when I play video from within XBMC I just get noise...

[fatez]

Confirmed!

On my Minimac intel 2ghz, AC3 with OSXBMC doesn't work :/


PS: With VLC -> yes

[iordonez]

Try setting this:

Open Applications/Utilties/Audio MIDI Setup

Select Properties for: Built-in Output
Then Select: Format 48000.0 Hz

That's what I had to do with Perian to get AC3 working and the setting I currently have for XBMC. Also make sure you are using an optical Audio cable...